A demand for high-definition images is increased along with an increase in the size of a screen of a television (TV). For this reason, ultra-high definition TV (UHDTV) broadcasting has been increasingly put into practical use. Japan, which has promoted UHDTV broadcasting, started 4K broadcast services utilizing a communication satellite (CS) and an optical line in 2015. Furthermore, the test broadcasting of UHDTV (4K and 8K) by a broadcast satellite (BS) will start in the future. Therefore, a variety of electronic devices compatible with 8K broadcasting have been developed (see Non-Patent Document 1). In practical 8K broadcasting, 4K broadcasting and 2K broadcasting (full-high vision broadcasting) will be also employed.
Not only televisions but also a variety of electronic devices that incorporate artificial intelligence utilizing artificial neural networks or the like have been developed. Artificial neural networks are expected to provide computers with higher performance than conventional Neumann computers. In recent years, a variety of researches on artificial neural networks realized with electronic circuits have been carried out. Non-Patent Document 2 discloses a technique relating to a chip having a self-learning function with artificial neural networks.
Furthermore, Patent Document 1 discloses an invention in which weight data necessary for computation with an artificial neural network is retained in a memory device including a transistor that contains an oxide semiconductor in a channel formation region.